IRS form used by foreign entities with U.S.-source income to document foreign status in regard to U.S. income tax, claim tax treaty benefits or exemption, and for FATCA purposes. The form is used to establish non-U.S. status, claim status as the beneficial owner of income, claim reduction in or exemption from tax withholding under chapter 3 of the U.S. tax code, and identify the entity’s category under chapter 4 (FATCA) of the code.